The present invention relates to helical coil insert power tools and in particular to an improvement in fixed carrier type power tools.
The invention pertains to a power tool for screwing a threaded insert into a threaded aperture of a workpiece. Hard material coil inserts are frequently utilized to provide a hard thread within a workpiece of soft material, such as aluminum. This practice is quite common, for example, in the aircraft industry where aluminum is used almost exclusively and high strength bonds are a necessity.
Various types of coil insert power tools are currently available. A first type includes a carrier that is adapted to retract from an advanced position as the mandrel is threadedly advanced in the opposite direction, causing insertion of the coil insert into the workpiece. Another type comprises a stationary "carrier" and a mandrel that is threadedly advanced relative to the fixed carrier. In the former type of power tool, adjustments in the depth of insertion of the coil insert are made by adjusting the position of a locking ring threadedly engaged with the carrier, which limits the retraction of the carrier and thereby limits the advancement of the mandrel. For an example of such a device, see U.S. Pat. No. 3,579,793, issued May 25, 1971, and assigned to the assignee of the present invention. With the fixed carrier type, however, the mandrel is the only moving element. Consequently, adjustments in the depth of insertion have heretofore been made by disassembling part of the tool and inserting shims within the interior of the tool to limit the advancement of the mandrel.
The present invention seeks to eliminate the necessity of having to dismantle a power tool of this type in order to make adjustments in its calibration. External adjustment means are provided in the power tool according to the present invention which, instead of directly limiting movement, adjusts the distance the mandrel must travel before reaching the workpiece. Accordingly, since the distance the mandrel advances is fixed, the effect is to vary the depth of penetration of the mandrel into the aperture of the workpiece.
The present invention, in general, comprises a power tool having a mandrel that is driven in rotation at one end by a motor and is threadedly engaged with a carrier fixedly secured to the body of the tool at its other end. When actuated by the motor, th threaded end of the mandrel advances longitudinally into a coil insert until a cam end thereof engages a tang at the end of the coil insert causing the insert to thereafter rotate with the mandrel. A threaded extension of the carrier abutting the workpiece reduces the diameter of the coil insert as it is screwed into the threaded aperture of the workpiece by continued advancement of the mandrel. Adjustments in the depth of insertion of the coil insert are made by adjusting the position of the carrier relative to the body of the tool. The position of the carrier is secured by a locking nut disposed between the carrier and the body of the tool which is tightened against the body once the desired carrier position is selected. Thus, since the end of the carrier abuts the surface of the workpiece, it can be seen that changes in the relative position of the carrier alters the depth of penetration of the mandrel into the aperture of the workpiece.
Additional objects and advantages of the present invention will become apparent from a reading of the following detailed description of the preferred embodiment which makes reference to the following set of drawings of which: